Known switching devices used in low voltage and medium voltage electric circuits, such as circuit breakers, disconnectors and contactors, are devices designed to allow the correct operation of specific parts of the electric circuits in which they are installed, and of the associated electric loads.
For the purpose of the present disclosure the term “low voltage” is referred to power applications with operating voltages up to 1000V AC/1500V DC, and the term “medium voltage” is referred to applications in the range from 1 kV up to some tens of kV, e.g. 50 kV.
Known switching devices can include a case housing one or more electric poles, each one having at least one movable contact and a corresponding fixed contact.
A driving mechanism causes the movement of the movable contacts between a first closed position in which they are coupled to the corresponding fixed contacts and a second open position in which they are spaced away from the corresponding fixed contacts.
The operation of the driving mechanism on the movable contacts is generally carried out through a main shaft which is operatively connected to the movable contacts; a kinematic chain of the driving mechanism causes the desired movement of the main shaft for opening or closing the switching device.
The driving mechanism may be manually actuated by an operator for causing the opening or the closure of the switching device, or the driving mechanism may be actuated by one or more protection devices, in the event that electrical faults or failures occur and the opening of the switching device is therefore specified, for example, when a short circuit or an electric overload occurs.
Further, the driving mechanism may be actuated for causing the opening or the closure of the switching device by one or more accessories, such as for example, a motor operated equipment (MOE) or coil actuators.
Various types of known locking devices can be operatively connected to one or more parts of the kinematic chain so as to indirectly act, through such kinematic chain, on the rotating shaft to lock the movable contacts in their open position, therefore preventing the re-closure of the locked open switching device. In this way, an operator may operate in a safe way on one or more parts of the electric circuit in which the switching device is installed.
Known locking devices can be configured only for visually signaling their actuation and therefore the locked status of the open switching device, for example, through the positioning of one or more of their components. Only operators close to the switching device may visually check such locked status.
Such a condition can be particularly disadvantageous when the switching device is located in a non-easy accessible location, or many switching devices are located at different distant locations in the electric circuit in which they are installed. For example, in a wind power generation plant switching devices are installed at the base or on the top of wind towers.
Therefore, although known solutions perform in a rather satisfying way, there is still reason and desire for further improvements.